Now, description will be given below of a conventional portable belt grinder with reference to FIGS. 13 and 14.
FIG. 13 is a right side view of a conventional portable belt grinder, and FIG. 14 is a plan view of the conventional portable belt grinder. A portable belt grinder 101 shown in these figures includes, in the rear lower portion of a main body 102 thereof, a drum-shaped drive pulley 106 which can be driven and rotated by an electric motor (not shown).
Also, an idle pulley 113 is rotatably disposed in the front lower portion of the main body 102 and, between the idle pulley 113 and drive pulley 106, there is wound an endless abrasive belt 115. As the drive pulley 106 is driven and rotated by the electric motor, the abrasive belt 115 is rotated in the direction of the arrow mark shown in FIG. 13. Here, between the drive pulley 106 and idle pulley 113, there is interposed a guide plate 116; and, the abrasive belt 115 is rotated on the lower surface of the guide plate 116. When the abrasive belt 115 is pressed against a member to be ground W, the surface of the member to be ground W can be ground by the abrasive belt 115.
And, the main body 102 includes, in one side surface thereof existing closer to the abrasive belt 115, an open portion 102e which can be used to replace the abrasive belt 115.
Also, the upper surface of the abrasive belt 115 is almost covered with the main body 102. And, the main body 102 includes, in a portion of the front end thereof, an exposure portion 102d in order to use the curved surface of the idle pulley 113 for grinding.
When carrying out a grinding operation using the present portable belt grinder 101, an operator may be generally situated in the rear of the main body 102 because the operator grips not only a main handle 102a disposed in the rear portion of the main body 102 but also a sub handle 102b disposed in the front portion of the main body 102.
FIG. 15 is a section view taken along the E-E line shown in FIG. 13. A portable belt grinder 101 shown in FIG. 13 includes, in the rear lower portion of a main body 102 thereof, a drum-shaped drive pulley 106 which can be driven and rotated by an electric motor (not shown).
Also, an idle pulley 113 is rotatably disposed in the front lower portion of the main body 102 and, between the idle pulley 113 and drive pulley 106, there is wound an endless abrasive belt 115. As the drive pulley 106 is driven and rotated by the electric motor in the direction of the arrow mark shown in FIG. 13 (in the clockwise direction), the abrasive belt 115 is rotated in the same direction (in the arrow mark direction). Here, between the drive pulley 106 and idle pulley 113, there is interposed a guide plate 116; and, the abrasive belt 115 is rotated on the lower surface of the guide plate 116. When the abrasive belt 115 is pressed against a member to be ground W, the surface of the member to be ground W can be ground by the abrasive belt 115.
And, the main body 102 includes, in one side surface thereof existing closer to the abrasive belt 115, an open portion 102e which can be used to replace the abrasive belt 115. Also, as shown in FIG. 15, on the inner wall 102j of the main body 102 situated on the opposite side to the open side thereof, there are integrally provided two rib-shaped projections 102k in such a manner that they are spaced from each other in the longitudinal direction of the main body 102 (in the moving direction of the abrasive belt 115); and on these two projections 102k, there is mounted a rectangular plate-shaped belt guide 125 by a screw (see FIG. 13) in such a manner that they are substantially parallel to the one side end edge of the abrasive belt 115. This guide belt 125 is made of a material (such as an iron plate) higher in hardness than the main body 102 and, when the abrasive belt 115 is moved laterally as shown by a dot and dash line in FIG. 15, the guide belt 125 receives the one side end edge of the abrasive belt 115 to regulates the lateral movement (shift) of the abrasive belt 115.
However, in the conventional portable belt grinder 101 shown in FIGS. 22 and 23, as described above, since the upper surface of the abrasive belt 115 is almost covered with the main body 102, in the grinding operation, in order to confirm the position of the abrasive belt 115, the operator must look into the open portion 102e formed in the side surface of the main body 102 or the exposure portion 102d formed in the front end portion of the main body 102. This means that it is difficult for the operator to confirm which position of the member to be ground W is currently being ground.
Also, the abrasive belt 115 can be moved laterally depending on the contents of the grinding operation during the grinding operation. Although the lateral movement of the abrasive belt 115 is restricted by the belt guide, the two end faces of the abrasive belt 115 in the longitudinal direction thereof respectively have a right-angled surface. Owing to this, when the abrasive belt 115 moves laterally as shown by a chain line in FIG. 12 and the side end edge thereof touches the belt guide, the abrasive belt 115 collides with the right-angled corner portions of the two end faces of the belt guide in the longitudinal direction thereof, the abrasive belt 115 can be broken. And, in the conventional portable belt grinder 101, there is also found another problem that, since the belt end portion is difficult to observe, the grinding operation is continued on without noticing the touch of the abrasive belt 115 with the belt guide, thereby lowering the life of the abrasive belt 115 greatly.